Lenses are commonly used in optical systems to direct and/or reconfigure light. In data communication systems, for example, lenses are used to direct and/or reconfigure light provided by a light source to a detector, optical fiber, or some other destination.
Lenses can be configured to act in a transmissive manner to allow at least a portion of the light that is output from the light source to pass through the lenses. However, another portion of the light from the light source can be reflected from the lenses. In some implementations, the reflected light can be directed to a back monitor photo detector that is configured to detect the amount of reflected light. The back monitor photo detector is configured to generate a signal corresponding to the amount of reflected light. The signal can be provided to a controller that adjusts the power of the light source to a desired power level. Typically, the desired power level is a constant power level. Maintaining a constant power level can be beneficial since some electrical and/or optical parameters of some light sources, such as lasers, can vary due to effects such as manufacturing tolerance, temperature, and aging. As such, control of the power level of the light source can enhance the performance of systems that use these light sources.
Various conventional techniques have been used to reflect light from lenses, such as, for example, to a back monitor photo detector. In one conventional approach, a tilted window (separate from the lens) is provided above the back monitor photo detector and the light source, where the tilted window includes a partially reflective coating. The tilted window reflects a portion of the light beam from the light source to the back monitor photo detector. Accordingly, in such an implementation, both a partially reflective window and a separate lens are provided in the path of the light beam. Having to manufacture and mount both of these separate components can increase the cost of the system. In addition, in some applications, there is insufficient room between the light source and the desired destination to accommodate both a partially reflective window and a separate lens.
Another conventional approach is to provide a concave lens that includes a transmissive part for passing a portion of an incident light beam and a reflective part for reflecting a portion of the incident light beam. The reflective part is preferably substantially non-transmissive. However, implementing a concave lens has various drawbacks, such as putting restrictions on the size and shape of lens that can be used for various applications. Therefore, concave lenses cannot be used in certain applications.
Accordingly, what is needed in the art is a reflective lens that overcomes drawbacks of conventional lenses discussed above.